From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 81CF3C433DB for ; Wed, 17 Feb 2021 14:08:15 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 0B85464DBD for ; Wed, 17 Feb 2021 14:08:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0B85464DBD Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 787758D0001; Wed, 17 Feb 2021 09:08:14 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 737F06B0070; Wed, 17 Feb 2021 09:08:14 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 600AD8D0001; Wed, 17 Feb 2021 09:08:14 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0036.hostedemail.com [216.40.44.36]) by kanga.kvack.org (Postfix) with ESMTP id 49AC46B006E for ; Wed, 17 Feb 2021 09:08:14 -0500 (EST) Received: from smtpin04.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 0935952D5 for ; Wed, 17 Feb 2021 14:08:14 +0000 (UTC) X-FDA: 77827939308.04.4ADC309 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) by imf05.hostedemail.com (Postfix) with ESMTP id 15277E0011EE for ; Wed, 17 Feb 2021 14:08:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1613570892; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=P8RxsF8J5nDa+mgXtHAOtJY50kcCIvzbpkGeCGDBzqw=; b=AKCuvn/0gcVrqQvRMbJ43BAaLhdTwqv73mVLPtmwYPCv4zfJKWOkr2qf9YywumHB850SVd B0EUNHlTlVIK3cEsVSuz8Q9LPXm8wocXh6cvGFQOu5fitjiUNwdS+trCsc2voUhha9MjkG FOXG5UHf8dL1TuA72gn8tSmWWyBliYk= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-487-OmuYUHRBNk-It2J9Wo7O9g-1; Wed, 17 Feb 2021 09:08:08 -0500 X-MC-Unique: OmuYUHRBNk-It2J9Wo7O9g-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id ED4C46D4F7; Wed, 17 Feb 2021 14:08:06 +0000 (UTC) Received: from [10.36.114.178] (ovpn-114-178.ams2.redhat.com [10.36.114.178]) by smtp.corp.redhat.com (Postfix) with ESMTP id 5911719C46; Wed, 17 Feb 2021 14:08:05 +0000 (UTC) To: Michal Hocko Cc: Oscar Salvador , Andrew Morton , Mike Kravetz , Muchun Song , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20210217100816.28860-1-osalvador@suse.de> <20210217100816.28860-2-osalvador@suse.de> <182f6a4a-6f95-9911-7730-8718ab72ece2@redhat.com> <5f50c810-3f49-a162-6d1d-cf621c515f45@redhat.com> From: David Hildenbrand Organization: Red Hat GmbH Subject: Re: [PATCH 1/2] mm: Make alloc_contig_range handle free hugetlb pages Message-ID: <5d70b340-2db0-ef1f-1564-e5d39354c11c@redhat.com> Date: Wed, 17 Feb 2021 15:08:04 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Stat-Signature: rhs3xud965in8u7pbqtnhwm3ocoezzm9 X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 15277E0011EE Received-SPF: none (redhat.com>: No applicable sender policy available) receiver=imf05; identity=mailfrom; envelope-from=""; helo=us-smtp-delivery-124.mimecast.com; client-ip=216.205.24.124 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1613570891-56227 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 17.02.21 14:59, Michal Hocko wrote: > On Wed 17-02-21 14:53:37, David Hildenbrand wrote: >> On 17.02.21 14:50, Michal Hocko wrote: > [...] >>> Do we have any real life examples? Or does this fall more into, let's >>> optimize an existing implementation category. >>> >> >> It's a big TODO item I have on my list and I am happy that Oscar is lo= oking >> into it. So yes, I noticed it while working on virtio-mem. It's real. >=20 > Do not take me wrong, I am not opposing to the functionality. I am > asking for the specific usecase. Makes sense, and a proper motivation should be included in the=20 patches/cover letter. So here comes a quick-n-dirty example: Start a VM with 4G. Hotplug 1G via virtio-mem and online it to=20 ZONE_MOVABLE. Allocate 512 huge pages. [root@localhost ~]# cat /proc/meminfo MemTotal: 5061512 kB MemFree: 3319396 kB MemAvailable: 3457144 kB ... HugePages_Total: 512 HugePages_Free: 512 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB The huge pages get partially allocate from ZONE_MOVABLE. Try unplugging=20 1G via virtio-mem (remember, all ZONE_MOVABLE). Inside the guest: [ 180.058992] alloc_contig_range: [1b8000, 1c0000) PFNs busy [ 180.060531] alloc_contig_range: [1b8000, 1c0000) PFNs busy [ 180.061972] alloc_contig_range: [1b8000, 1c0000) PFNs busy [ 180.063413] alloc_contig_range: [1b8000, 1c0000) PFNs busy [ 180.064838] alloc_contig_range: [1b8000, 1c0000) PFNs busy [ 180.065848] alloc_contig_range: [1bfc00, 1c0000) PFNs busy [ 180.066794] alloc_contig_range: [1bfc00, 1c0000) PFNs busy [ 180.067738] alloc_contig_range: [1bfc00, 1c0000) PFNs busy [ 180.068669] alloc_contig_range: [1bfc00, 1c0000) PFNs busy [ 180.069598] alloc_contig_range: [1bfc00, 1c0000) PFNs busy I succeed in unplugging 540MB - 484 MB remain blocked by huge pages=20 ("which did not end up there by pure luck"). These pages are movable=20 (and even free!) and can easily be reallocated. --=20 Thanks, David / dhildenb